In commercial systems for making certain processed meat products such as bologna and hot dogs, raw meat in the form of chunks or pieces and other ingredients such as spices are ground, chopped and/or otherwise blended with one or more salt solutions or brine to provide a mixture that can subsequently be formed into a stable meat emulsion or protein matrix. Similar steps of grinding, chopping and/or otherwise working are also employed in making coarse ground products such as sausages, whole muscle products such as processed ham and processed turkey, and other processed meat products. In each case, protein forms a matrix to hold or bond the separate pieces together.
A stable protein matrix requires the protein bonds to suspend or bond with fat and water. Creation of protein bonds in this context requires a process commonly known as protein extraction. In this process, salt soluble or salt-extractable and heat coagulable proteins such as myosin, actomyosin, and actin bind water, swell and become tacky as a result of working or blending of the meat in the presence of a salt or a salt solution. The proteins are subsequently set when heated to create a bond. Other myofibrillar proteins, as well as sarcoplasmic or water soluble or extractable proteins, may also play a role in bonding. Salt solutions that may be used in protein extraction include, but are not limited to, sodium chloride, sodium pyrophosphate or diphosphate, potassium chloride, sodium lactate, and potassium lactate. In protein extraction as described herein, the mechanism believed to be primarily responsible for creation of the bonds involves binding proteins, salts, fats, and/or water and subsequent swelling of the proteins, rather than solution of the proteins. More precisely, it is believed that the salt solution frees bonding sites on the proteins for bonding with each other, as well as with water and fat. The particles of the cooked product are bound to each other by the proteins to provide integrity to the final meat product.
As used herein, a stable meat protein matrix refers to a mixture that retains a large percentage of its components during further processing, including cooking, and during its shelf-life as a final product. For instance, an emulsion is considered stable if less than 2% of the product weight is lost due to fat cook-out from the cooking stage. If the protein matrix is unstable, either it or the final product will lose excessive quantities of water or fat. An unstable protein matrix leads to yield loss and to a final product that is not able to maintain sufficient integrity over its desired shelf-life.
Conventional batch processing is a lengthy process requiring a number of discrete steps. Initially, various meats are provided by a vendor with specified contents. More specifically, the meats are provided with a specified protein, fat, and/or water content, typically a percentage by weight. A batch sheet is provided to processing plant personnel indicating what mixture of meats, water, and additives are to be combined for one of a variety of meat products.
Though purchasing is done outside of the processing plant, the batch sheet is based on knowledge of the meats presently on-hand at the plant. However, the batch sheet often needs to be adjusted. For instance, a particular vendor may provide meat rated as 70% protein, while the actual meat has a slightly different content such as 68% protein. Because the batch sheet is based on the purchasing and the meat rating provided by the vendor, the plant personnel often have to adjust the meats selected for the meat product based on the formula desired for the final product. The final product mixture is carefully controlled. For instance, a particular product, such as hot dogs, may have no more than 30% fat by weight. If a particular meat is utilized where the fat content is greater than what the batch sheet calls for, the final product may have an excessive amount of fat. To avoid this, the plant personnel would increase the protein provided by other meats to balance the fat content.
Unfortunately, this is not necessarily a sufficiently precise approach. Each meat, as well as each chunk in a batch of meat, may vary significantly from a sample taken and assumed to be average. Once the water and other additives are mixed in with the batch, it may be difficult to alter the balance. At times, the resulting batch is determined to be inaccurately mixed, and remedial procedures must be taken such as mixing the batch in with additional correction materials. In order to reduce the likelihood of an imprecise batch, relatively large quantities of meat are provided for a single batch in hopes of minimizing or driving to a mean the composition deviation resulting from a meat portion with an aberrational content. A typical amount of a particular meat for a batch is approximately 2000 lbs.
Batch processes for blending meat and other ingredients and extracting protein are well known. A known method for achieving protein extraction and ingredient blending for whole muscle products such as processed turkey and processed ham involves puncturing the whole muscle meat with hypodermic type needles, injecting brine through the needles, and using a batch processor or mixer to work the meat for approximately 45 minutes under vacuum to remove air, as discussed below. For coarse ground and emulsified products, meat is ground and added to a batch processor with water, salt solution, spices, and/or other ingredients and worked with or without vacuum for up to an hour, or e.g., 15 to 45 minutes.
A large batch mixer may process approximately 6,000-12,000 pounds per hour. The meat product constituents including the meats and the additives are combined in the low shear batch mixer. This mixing stage typically requires 30-60 minutes of being mixed. It is during this time that the constituents are transformed into a mixture that will form a stable protein matrix.
A stable protein matrix is formed when mixtures for each of whole muscle products, coarse ground products, and emulsified products allow the salt solution to reach the salt-extractable protein. This process, known as curing, achieves the protein extraction. For whole muscle products, injection with needles inserted into the meat chunks to deliver the brine solution is a relatively imprecise method for attempting to reduce a distance of the meat through which the salt solution must diffuse. The curing stage typically requires 24-48 hours for satisfactory diffusion, and the batches are stored in vats placed in coolers for the cure time. Once the protein extraction has occurred, the mixture may then be further processed.
Input constituents are calculated to result in a specific quantity of cooked product. If excessive water or fat is lost post-mix such as during the cook stage, the carefully regulated water, fat, and meat ratios will be off-target. If fat is lost prior to the cook stage, it often remains in the machinery or piping through which the mixture is processed. This can result in down time for the machinery, likelihood of damaged machinery, and greater labor in cleaning the machinery. Furthermore, cooked emulsified products rely, to some degree, on non-protein or non-bound materials to provide the proper texture. The proteins bind to form a matrix with each other and, in the absence of sufficient fat or water, these bonds may form a larger, stronger matrix, which leads the product to become somewhat rubbery. Conversely, if there is too much water, the cooked product may be too soft, and may lack integrity.
As used herein, the term additives may refer broadly to brine solution, water without salt, a spice slurry, nitrite, or other additives. Though the brine solution and the meats themselves each include water, the balance for the final product is typically adjusted with a quantity of water. The spice slurry provides, for instance, flavorings. One additive is typically nitrite which is used as a preservative and to provide a desired color. Other inert additives, such as corn starch or non-functional proteins, may also be included.
As the mixture constituents are churned in the mixer for up to an hour, contact with air may produce a froth on the surface of the meat pieces. A final product having visible air may be unacceptable. In some cases, the product must be re-processed and mixed in with subsequent batches. Air in the product may appear as surface bubbles, or as surface holes. Entrapped air may also lead to product swelling during cooking, or may lead to the product having visible air bubbles within its interior.
Air affects the product in other ways, as well. For instance, some proteins are denatured by the presence of air, which reduces the functionality of the meat for binding fat and water. The air can also react with the nitrite to retard the development of the proper color. The resulting color may then be undesirable or objectionable to consumers.
To avoid air being stirred into the mixture, vacuum pressure may be applied during the mixing process. This requires an extensive set up including the vacuum itself and seals to maintain the pressure. The vacuum system and seals require maintenance, and occasionally leak which results in downgraded product.
While such mixers have been used commercially for many years, they have significant drawbacks. For example, one of the problems is that air may undesirably be drawn into the product. Other drawbacks for the mixers include their space requirements and cost due to their large size, labor costs, the length of time required for processing each batch, vat handling and transfer yield loss, and the time and expense associated with cleaning of the apparatus.